Fume Hoods
Safety is the primary function of fume hoods. Proper performance and use of the fume hood are essential in providing safety to the user and other laboratory personnel. They exhaust toxic, flammable, noxious, or hazardous fumes and vapors by capturing, diluting, and exhausting these materials through the ductwork. If used correctly, fume hoods also provide spill containment and physical protection against fire and explosion.
How Fume Hoods Work
A fume hood is a ventilated enclosure in which gases, vapors, and fumes are contained. An exhaust fan on the top of the laboratory building pulls air (and airborne contaminants) through connected ductwork and exhausts them to the atmosphere.
UT Dallas has two types of fume hoods on campus:
- Constant volume (CV): where the quantity of air pulled through the hood is constant. When the sash is lowered, the velocity of airflow through the hood increases proportionally; thus, higher face velocities can be obtained by lowering the sash. Because the exhaust fan must run at a constant rate, this type of fume hood can be wasteful of energy when the fume hood is not in use.
- Variable air volume (VAV): where the quantity of air pulled through the hood varies as the sash is adjusted to maintain a set face velocity. Therefore, when the sash is lowered, the velocity of airflow through the hood stays the same. This type of fume hood is preferred for energy savings.
When to Use a Fume Hood
Fume hood use should be based on a risk assessment of the intended procedure. This assessment should consider characteristics of the materials used, experimental procedure, and skill and expertise of the user(s).
When should I contact Risk & Safety about my fume hood?
If any (or all) of the following is noticed, please contact the Office of Institutional Risk & Safety at safety@utdallas.edu, 972-883-7200, or through an incident report form.
If the current inspection sticker is missing, but the hood is not tagged out of service
- If the Kim-wipe test fails
- If the light in the fume hood is not working
- If you do not hear the fume hood motor running
- If you smell fumes or vapors when working in the hood
- If the hood has been relocated
- If you have a new hood in your lab
How do I know my fume hood has passed certification?
Fume hoods that pass annual certification will have information on a sticker located on the frame of the hood. A valid certification sticker should have the date of inspection (within the last year), identifying information for the inspector, and the average face velocity. An example of a fume hood sticker is displayed below. If you notice that the certification sticker is missing or torn, but the fume hood is not tagged out of service, please email safety@utdallas.edu.
How do I know if my fume hood failed certification?
Fume hoods that fail certification are tagged out of service. A sign similar to the one displayed below is posted on the sash of failed hoods. Please DO NOT remove this sign OR use the fume hood tagged out of service until repairs are complete and the hood is recertified. It is the responsibility of the PI and laboratory personnel to ensure the fume hood is working properly. If you notice that a fume hood is not working, contact the Office of Institutional Risk and Safety.
Fume Hoods vs. Biosafety Cabinets
Occasionally, both fume hoods and biosafety cabinets are referred to as “hoods” and can be found next to each other in the same laboratory. This can be misleading, as these two pieces of equipment serve different purposes. Make sure you are using the proper containment equipment for your work.
| Chemical Fume Hood | Biological Safety Cabinet |
| Used for hazardous chemicals | Used for infectious biological agents |
| Protects the user | Protects the user, environment, and material |
| No HEPA filter | Exhaust is HEPA filtered |
| Exhausts air outside the building | Exhausts air back into the room (usually) |
Proper Work Practices
The level of protection provided by a fume hood is affected by how the fume hood is used. No fume hood, however well designed, can provide adequate containment unless good laboratory practices are used, as follows:
- Check the hood survey sticker to ensure that the hood has been certified within the last year.
- Check the hood flow indicator and compare its reading to the reading indicated on the hood survey sticker. If the reading differs significantly from that on the sticker, the hood may not be operating properly.
- Before use, open the fume hood sash and allow the hood to run for at least five minutes to reach an appropriate flow rate.
- Mark a line with tape 6 inches behind the sash and keep all chemicals and equipment behind that line during experiments. This will help keep materials from escaping the hood when disturbances, like air currents from people walking past the hood, interfere with airflow at the face of the hood.
- Keep the sash at the level of the MAXIMUM SAFE SASH HEIGHT sticker (usually 18 inches) any time an experiment is in progress.
- Keep the sash completely lowered any time an experiment is in progress AND the hood is unattended.
- Extend only hands and arms into the hood and avoid leaning against it.
- Do not block baffles. If large equipment must be placed in the hood, put it on blocks to raise it approximately 2 inches above the surface so that air may pass beneath it.
- Do not use the hood as a storage device. Keep only the materials necessary for the experiment inside the hood. If chemicals must be stored in the hood for a period of time, install shelves on the sides of the hood, away from the baffles.
- The fume hood alarm will sound when the flow rate dips to unsafe levels. This can happen when the sash is lifted above the maximum safe sash height. Instead of silencing the alarm, try lowering the sash. If the alarm sounds when the sash is at a safe level, close the sash, push the Emergency Purge button, and contact Risk & Safety.